So, here's the thing. The picture above IS NOT a sea urchin expelling "guts through its mouth."
The author may have been might be thinking of sea cucumbers which expel their guts with great gusto! Here's a thing I wrote about that.

So, what is this a picture of?? This is an ANAL CONE at work! In other words, this is the sac that expels waste from the animal.
This is a structure that is found on the "top" surface of the urchin. Note that the mouth is found on the underside facing "downward" AWAY from its anus and the anal cone.All those little pellets in the sac? Yup. THAT is sea urchin feces. This is the first good picture I have seen which so clearly shows the scatalogical functions of the anal cone! WOO!Yay the things you learn here!

So you know that offset plate that you see on the top of a starfish? I wrote a whole post about them here. In sea urchins they are part of what's called the APICAL SYSTEM that is found on the top of the animal.

About Me

I pursue starfish related adventure around the world with a critical eye and an appreciation for weirdness.
Support has been courtesy of the National Science Foundation but the views and opinions presented herein are mine and do not reflect the opinions of them or any affiliated institutions.
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